Generally, a drum-type washing machine is a kind of washing machine that performs a washing operation using the friction between a drum, which is rotated by a driving force of a motor, and laundry put in the drum and using impact applied to the laundry when the laundry drops, under the condition that detergent and wash water are also put in the drum. The drum-type washing machine has various effects in that damage to the laundry is minimized, the laundry is not entangled, and the laundry is struck and rubbed.
In a pulsator-type washing machine, which is another kind of washing machine, on the other hand, a spin-drying tub is mounted in a water storage tub, in which water is stored, and a washing operation is performed under the condition that laundry is submerged in wash water supplied into the spin-drying tub. As a result, the pulsator-type washing machine uses a large amount of wash water.
The pulsator-type washing machine performs a washing operation using the friction between the wash water and the laundry caused by the rotation of the spin-drying tub or a pulsator mounted below the spin-drying tub for generating a water current and using the action of detergent.
Specifically, in the drum-type washing machine, the rotation axis of the drum is substantially parallel with the ground, and therefore, the laundry can be dropped and washed even when a small amount of wash water is stored in a tub and the drum. In the pulsator-type washing machine, on the other hand, the rotation axis of the spin-drying tub is substantially perpendicular to the ground, and therefore, the laundry can be washed only after the wash water is supplied to the water storage tub such that the laundry is fully submerged in the wash water.
In the conventional pulsator-type washing machine, even the upper part of the water storage tub is submerged in the wash water as described above. Such submergence is repeated whenever the washing machine is operated. Since the water storage tub is not driven, pollutants or scale may be accumulated on the entire inner circumferential surface of the water storage tub as well as the lover part of the water storage tub. With the passage of time, the pollutants or the scale may decompose with the result that the pollutants or the scale may give off a bad smell or the laundry may be polluted by the pollutants or the scale.
For this reason, there have been proposed various methods of cleaning the inner circumferential surface of the water storage tub of the conventional pulsator-type washing machine. Nevertheless, it is not easy to clean the water storage tub using a strong water current obtained by rotating the spin-drying tub at high speed while the wash water is stored in the water storage tub.
This is because, when the spin-drying tub is rotated at high speed, excessive load is applied to a motor due to the friction between the wash water and the outer circumferential surface of the spin-drying tub. Even if the spin-drying tub is rotated at very high speed, it is difficult for the wash water to reach the upper side part of the inner circumferential surface of the water storage tub.
In the conventional pulsator-type washing machine, therefore, the water storage tub is cleaned using special detergent during a general washing or rinsing operation.
For this reason, the detergent used to clean the water storage tub has a stronger cleaning force than detergent used to perform the general washing operation. Specifically, the detergent used to clean the water storage tub contains a large amount of chemical components causing water pollution, and therefore, the detergent used to clean the water storage tub is not environmentally friendly.
FIG. 1 is a view schematically illustrating the construction of a conventional drum-type washing machine. Hereinafter, the construction of the conventional drum-type washing machine will be described in brief with reference to FIG. 1.
As show in FIG. 1, the drum-type washing machine includes a cabinet 1 having a laundry inlet hole formed in the front part thereof, a door 2 mounted at the cabinet 1 for opening and closing the laundry inlet hole, a tub 10 mounted in the cabinet 1 for storing wash water, a motor 4 mounted to the tub 10 for generating a driving force, a washing shaft 5 connected to the motor 4, and a drum 6 connected to the washing shaft 5 for washing laundry using the driving force transmitted from the motor 4.
The tub 10 is supported by a damper 11 and a spring 23. The damper 11 and the spring 23 serve to absorb vibration generated when the motor 4 and the drum 6 are rotated.
The motor 4 includes a rotor (not shown) and a stator (not shown).
In the drum-type washing machine with the above-stated construction, wash water is supplied such that the lower part of the tub 10 and the lower part of the drum 6 are submerged in the wash water, unlike the previously described pulsator-type washing machine. And only some of the wash water stored in the lower part of the tub 10 is raised together with the laundry by lifters (not shown) mounted inside the drum and then drops.
According to the washing manner of the drum-type washing machine, therefore, opposite side parts of the inner circumferential surface of the tub and the upper side part of the inner circumferential surface of the tub are not submerged in the wash water, unlike the pulsator-type washing machine.
In the conventional drum-type washing machine, therefore, the probability that pollutants or scale may be accumulated at the opposite side parts of the inner circumferential surface of the tub, particularly, the upper side part of the inner circumferential surface of the tub is not considered. As a result, the necessity for cleaning the pollutants or the scale accumulated at the opposite side parts of the inner circumferential surface of the tub, particularly, the upper side part of the inner circumferential surface of the tub, has not come to the front.
Meanwhile, even though the term “the cleaning of the tub” is used in the conventional drum-type washing machine, this term does not mean the cleaning of the opposite side parts of the inner circumferential surface of the tub, particularly, the upper side part of the inner circumferential surface of the tub. In other words, this term means only the cleaning of the lower side part of the inner circumferential surface of the tub.
However, the inventor of the present invention has found that the pollutants and the scale may be accumulated at the opposite side parts of the inner circumferential surface of the tub and the upper side part of the inner circumferential surface of the tub as well as the lower side part of the inner circumferential surface of the tub, and therefore, the accumulated pollutants or the accumulated scale gives off a bad smell, and furthermore, laundry is polluted by the pollutants or the scale.
Consequently, a method of easily cleaning the entire inner circumferential surface of the tub without using an additional cleaning device for cleaning the tub has been studied.
In addition, the conventional drum-type washing machine is essentially provided with a gasket mounted between the door and the tub for preventing the leakage of the wash water. However, there is much possibility that pollutants are accumulated at the lower part of the gasket due to the sectional shape of the gasket. And these pollutants are not easily visible unless a user deforms the gasket to turn the gasket inside out. Consequently, it is not easy to remove the pollutants from the gasket.
For this reason, a method of easily cleaning the gasket without using an additional cleaning device for cleaning the gasket has been also studied.